Fast ascent question..

This is somewhat related to the losing your weightbelt question.

Lets say I'm nowhere near my NDL limit.. everyone knows those risks. Lets say I also Zzzzz or ahhhh or "oh shiiiii.." my way to the surface to make sure my lungs don't have problems.

What other risks might there be for a quick ascent? I'm wondering what else I should be concerned about if I have a quick ascent for whatever reason.

For example, if I'm at a training platform at 25 feet and I want to test flaring out as a result of a lost weightbelt.. would that be overly dangerous, or as long as I remember to breath out I should be fine?

Just wondering if there's some risk I'm not thinking about. I'd like to test emergency scenarios before they happen, but not if it would be stupid

I have a case history for you. (no names to repsect privacy)
Diver makes a dive at 12:30 pm to 35 feet for 25 minutes.
Surface interval 2hours 45 inutes.
Diver makes second dive to 65 feet.
His dive time 25 minutes.
He's in a curent , breathing faster than expected.
He looses his buddy.
He runs out of air.
He makes a successful ESA. (faster than 30 ft/second)
His buddy surfaces 5 minutes later (normal ascent including 3 min stop at 15 feet).
4 hours later the ESA diver feels extreme fatique and lays down for nap. He wakes up about 7 pm with pain in his shoulder, cold sweats and feels like he going to throw up.
The diver went to the emergency, and was put on oxygen and transported to a (3 hours away ) recompression chamber where they drew blood gasses and treated him for Class 1 DCI. He made a full recovery.

You can run the tables yourself and see that both divers are well within deco limits, even though they dived the deeper dive 2nd.
The buddy had no symptoms even though he was down 5 minutes longer.

It would seem clear the rapid ascent caused his DCI.

Mike D

Some tissue absorbs nitrogen very fast and if you do a rapid ascent they will still release bubbles in your bloodstream and may cause DCS. While the risk is higher if you get closer to your NDL, it is still very significant even if you have only a few minutes of bottom time.
Why do you want to practise flaring? Just make sure you never loose your weight belt.
ScubaRon

Firstly even "nowhere near NDL" may be a bit misleading as every dive absorbs some nitrogen and releasing it quickly in an ascent can cause bubble formation and problems.
NDLs are calculated assuming a known and specific ascent rate. A faster rate could put someone over the NDLs for that reason.

As well as the breathing out for embolism reduction chances dont forget things like the speed at which you'll need to clear ears to avoid a reverse block.

I wouldnt practice belt release/flare in >10ft of water really. Better yet, try a nice 12ft pool. You still get time to flare.

Ceberon once bubbled...
Just wondering if there's some risk I'm not thinking about. I'd like to test emergency scenarios before they happen, but not if it would be stupid

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In addition to "loss of weightbelt", at least two other possible emergency scenarios have high probabilities of rapid ascents: emergency swimming ascent and stuck-on power inflator.

I practiced stuck-on power inflator in shallow water, at the beginnning of a dive. As others have noted, you can do the weightbelt/flaring practice at very shallow depths in a pool.

ESA I also practiced at the very beginning of a dive, and in addition, I halted my ascent once I had gone from 90' to around 20'. I assumed that I was bubbling and redescended immediately, and stayed at depth for a minimum of 30 minutes with ultra careful ascent. (The time at depth and ultra long ascent time are to reabsorb any bubbles that may have formed)

Were I to repeat my practice of ESA, I would prebreath 36-40% nitrox for at least 15 minutes before doing the skill (kind of like aviators prebreath O2 before experiencing explosive decompression in an altitude chamber). Again, I would do it immediately upon descending, and halt it before reaching the surface.

At some point, the skills practice becomes more dangerous than the emergency scenario you are training for. Doing the ESA a second time just to convince me that the first one wasn't a fluke was enough for me ---- I will probably never ever do it again.

Ceberon once bubbled...
For example, if I'm at a training platform at 25 feet and I want to test flaring out as a result of a lost weightbelt.. would that be overly dangerous, or as long as I remember to breath out I should be fine?

Just wondering if there's some risk I'm not thinking about. I'd like to test emergency scenarios before they happen, but not if it would be stupid

Click to expand...

15 ft would be a better maximum depth to perform these independent studies activities. You may want to have your buddy watch you from the surface, and of course off to the side.

With the exception of habitat saturation diving, which is not normally a relevant topic on this board, you can normally stay at 20 ft depth indefinitely, on scuba, and return to the surface without a safety or deco stop from there.

The NOAA Diving Manual begins to reflect NDL limitations at 25 ft.

CESA/ESA (PADI calls it CESA / NAUI calls it ESA) is a good skill to practive in the open water, at 15 to 20 ft depth. Remember the preparatory steps:

1) Establish neutral buoyancy, either by hovering, or by a fin pivot, or however you get yourself neutrally buoyant;

2) Keep your 2nd stage in your mouth at all times;

3) Keep your weight belt ON;

4) Kick up to begin your ascent, and continue to kick slowly and solidly all through your ascent;

5) Humm or whatever to ensure your airway is open, and never hold your breath;

6) Orally inflate your B/C the moment you reach the surface;

7) If you need to, ditch your weights at the surface, to ensure positive buoyancy, if your oral inflation of your B/C did not go as well as desirable.

The main advantage of the CESA/ESA is that it is a controlled ascent.

If you are going to practice the EBA (ditching of your weights underwater), then I would suggest you limit this drill to the pool, not in the open water.

You can also practice putting your weight belt on properly, exhaling completely before you tighten it around your waistline, and tightening it again at depth, if necessary, to make sure it is tight before you begin your dive touring.

I agree flaring is one of the things you need to do to slow your ascent rate with a lost weight belt and it is very effective, but I also agree there is not a lot of need to practice it. Remembering to do it will be the big challenge and if you feel practice helps in that regard then limit it to 15 ft. or so.

As for a stuck inflator (drysuit or BC), just disconnect the hose to the offending unit. It is not an emergency that requires an immediate ascent to the surface controlled or otherwise. Often the problem can be fixed underwater and the dive can be completed normally. If not, you can still orally inflate a BC or, in a dry suit, you can continue the dive to your exit point as long as you only ascend and do not try to go deeper where you may develop a squeeze and/or excessive negative bouyancy.

It's not that I'm necessarily interested in testing out losing my weight belt, etc etc. I understand flaring isn't rocket science. I simply was thinking about stories I'd read, and was wondering. I know I breath out automatically when I'm going up, and I can clear my ears plenty fast (I can keep my jaw cracked so I automatically adjust).

I just know that any book you read will say "Don't ascend fast", rather than "If you are at 12' and you've only been down for 5 minutes, and you "ahhh" on the way up, you should be safe to ascend at any speed". I'm simply a curious person

I also know when people are doing training of DM's, they simulate runaway ascents, etc, and I was wondering what risk the instructors may be under if they simulate a runaway ascent and end up going up pretty fast..

Ceberon once bubbled...
(I can keep my jaw cracked so I automatically adjust).

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I tend to keep my jaw a solid one piece thing...it helps with consumption of beer

Ceberon once bubbled...
I also know when people are doing training of DM's, they simulate runaway ascents, etc, and I was wondering what risk the instructors may be under if they simulate a runaway ascent and end up going up pretty fast..

Click to expand...

D/Ms are normally positioned behind BOW (Basic Open Water) students, so that if the student bolts to the surface, and the instructor grabs the student, then the D/M can grab the instructor and assist with the restraint. That way you DONT end up with a run-away ascent problem. But only the instructor is allowed by most agency standards to restrain a student from ascending. A D/M is not.

D/Ms are sometimes positioned above AOW (Advanced Open Water) students on deep dives, to intercept them and assist them, if they lose control of their buoyancy and start to head to the surface. However if an AOW student truly wants to surface, it is his/her right, and a D/M should not prevent them. Help them get control of their ascent and slow it down, yes. Prevent them, no. AOW students are certified divers and are supposed to know what they are doing.

In training D/Ms to help with restraints, you normally train them to restrain the instructor NOT the student. D/Ms would first learn when and how to restrain students in an ITC/IDC. However some instructors may teach differently, or have different agency standards.

Ascents from 60 ft depth or less should be no faster than 30 ft per minute, which is one foot every 2 seconds, as in "one thousand one, one thousand two."